package com.tscnd.core.security;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.springframework.security.access.SecurityMetadataSource;
import org.springframework.security.access.intercept.AbstractSecurityInterceptor;
import org.springframework.security.access.intercept.InterceptorStatusToken;
import org.springframework.security.web.FilterInvocation;
import org.springframework.security.web.access.intercept.FilterInvocationSecurityMetadataSource;

/**
 * 该过滤器的主要作用就是通过spring著名的IoC生成securityMetadataSource。
 * securityMetadataSource相当于本包中自定义的MyInvocationSecurityMetadataSourceService。
 * 该MyInvocationSecurityMetadataSourceService的作用提从数据库提取权限和资源，装配到HashMap中，
 * 供Spring Security使用，用于权限校验。
 * @author sparta 11/3/29
 *
 */
public class MyFilterSecurityInterceptor extends AbstractSecurityInterceptor implements Filter {
	//其他的两个组件，已经在AbstractSecurityInterceptor定义  
    private FilterInvocationSecurityMetadataSource securityMetadataSource; 
    
    
    
    
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		FilterInvocation fi = new FilterInvocation(request, response, chain);  
        invoke(fi);  
		
	}
	/*
	 * 最核心的代码就是invoke方法中的InterceptorStatusToken token = super.beforeInvocation(fi);
	 * 这一句，即在执行doFilter之前，进行权限的检查，而具体的实现已经交给accessDecisionManager了，
	 */
    private void invoke(FilterInvocation fi) throws IOException, ServletException {  
        // object为FilterInvocation对象  
                  //super.beforeInvocation(fi);源码  
        //1.获取请求资源的权限  
        //执行Collection<ConfigAttribute> attributes = SecurityMetadataSource.getAttributes(object);  
        //2.是否拥有权限  
        //this.accessDecisionManager.decide(authenticated, object, attributes);  
        InterceptorStatusToken token = super.beforeInvocation(fi);  
        try {  
            fi.getChain().doFilter(fi.getRequest(), fi.getResponse());  
        } finally {  
            super.afterInvocation(token, null);  
        }  
    }

	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}

	@Override
	public Class<? extends Object> getSecureObjectClass() {
		// TODO Auto-generated method stub
		return FilterInvocation.class;
	}

	@Override
	public SecurityMetadataSource obtainSecurityMetadataSource() {
		// TODO Auto-generated method stub
		 return this.securityMetadataSource;  
	}

	
	public void setSecurityMetadataSource(
			FilterInvocationSecurityMetadataSource securityMetadataSource) {
		this.securityMetadataSource = securityMetadataSource;
	}

	public FilterInvocationSecurityMetadataSource getSecurityMetadataSource() {
		return securityMetadataSource;
	}

	
	
	
}
